Wireless in-band signaling with in-vehicle systems

ABSTRACT

This invention pertains to methods and apparatus for data communications from vehicles, to obtain emergency, concierge and other services, using a voice channel of a digital wireless telecommunications network. Signaling is described for commencing data sessions after establishing a voice channel call. The call may be initiated from the vehicle automatically, and the call taker location may be unattended. Signaling methods are selected for traversing both newer and legacy vocoders for ubiquitous operation.

RELATED APPLICATIONS

This application claims priority from U.S. provisional patentapplication 60/981,487, filed Oct. 20, 2007.

COPYRIGHT NOTICE

© 2007-2008 Airbiquity Inc. A portion of the disclosure of this patentdocument contains material which is subject to copyright protection. Thecopyright owner has no objection to the facsimile reproduction by anyoneof the patent document or the patent disclosure, as it appears in thePatent and Trademark Office patent file or records, but otherwisereserves all copyright rights whatsoever. 37 CFR §1.71(d).

TECHNICAL FIELD

This invention pertains to methods and apparatus for data communicationsfrom vehicles, to obtain emergencies, concierge and other services,using a voice channel of a digital wireless telecommunications network.

BACKGROUND OF THE INVENTION

Wireless telecom coverage has become nearly ubiquitous in much of theworld, especially in industrialized countries. However, in manydeveloping countries as well, whole regions that lack traditionalcopper-wired telecom infrastructure have skipped over that technology todeploy wireless instead. Modern wireless networks provide a range ofvoice and data services. Technical details of those services can befound in many places, for example, the 3GPP standards group web sitewww.3gpp.org.

Some wireless data services, however, are slow, and coverage is spotty.Wireless voice services, by contrast, tend to be of good quality and areavailable almost everywhere people travel. We refer to “in-band”communications as meaning in the voice channel, as distinguished from adata channel, control channel or other non-voice wireless service. Voicechannels are characterized by special performance characteristics. Forexample, only a relatively narrow range of audio frequencies needs to betransceived, based on the normal human voice. In fact, sophisticatedcompression and coding techniques are known to enable sending andreceiving human voice very efficiently over digital wireless networks.However, these voice coders or “vocoders”—typically implemented insoftware, DSP chips and the like—do not transmit non-voice sounds wellat all. To the contrary, they are carefully designed to filter outnon-voice signals.

Related information can also be found in U.S. Pat. No. 6,144,336incorporated herein by this reference. Additional disclosure can befound in U.S. Pat. No. 6,690,681 also incorporated by reference. Andfinally, further relevant disclosure appears in U.S. Pat. No. 6,493,338also incorporated by reference as though fully set forth. The foregoingpatents are owned by the assignee of the present application.

Additional aspects and advantages of this invention will be apparentfrom the following detailed description of preferred embodiments, whichproceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram illustrating the typical speechpath for a wireless voice call; i.e., a telephone call over the wirelesstelecommunications network.

FIG. 2 is a simplified block diagram of an illustrative In-VehicleSystem (IVS).

FIG. 3 is a diagram illustrating progress over time of an in-band modemdetection scheme.

FIG. 4 is a diagram illustrating progress over time of an improvedin-band modem detection scheme applying a frequency modulated tone inaccordance with one embodiment of the invention.

FIG. 5 is a diagram illustrating progress of a backward-compatibleserver transmitting both types of initiating signal and listens for bothtypes of response signal. In this way it will be able to identify theIVS modem type.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a simplified block diagram illustrating the typical speechpath for a wireless voice call; i.e., a telephone call over the wirelesstelecommunications network. Analog voice signals from a microphone 11are digitized by an A/D converter 12, and then fed to a vocoder 14encoding algorithm (at 8000 samples/sec). The encoder 16 producespackets of compressed data (typically one packet per 20-ms frame ofaudio) and feeds this data stream to a radio transmitter of a radiotransceiver 18. On the other side, a radio receiver passes the packetsto the decoding algorithm 17, which then reconstructs (imperfectly) theoriginal voice signal as a PCM stream. This PCM stream is eventuallyconverted back into an analog voltage which is then applied to a speaker19.

Using this type of system, modest amounts of data (here we mean userdata, not vocoder speech data) can be transmitted “in-band” throughcareful selection of frequencies, timing, and the use of specialtechniques that “trick” a vocoder into transmitting information bymaking that information “look like” human voice data. This type of datacommunication, using the voice channel of a wireless system, issometimes called “in-band signaling.” It can be implemented in hardwareand or software referred to as an “in-band signaling modem,” borrowingthe old modem term (modulator-demodulator) familiar in traditional “landline” telecommunications.

Several issued patents disclose in-band signaling technology thatcommunicates digital data over a voice channel of a wirelesstelecommunications network. In one example, an input receives digitaldata. An encoder converts the digital data into audio tones thatsynthesize frequency characteristics of human speech. The digital datais also encoded to prevent voice encoding circuitry in thetelecommunications network from corrupting the synthesized audio tonesrepresenting the digital data. An output then outputs the synthesizedaudio tones to a voice channel of a digital wireless telecommunicationsnetwork. In some cases, the data carrying “tones” are sent along withsimultaneous voice. The tones can be made short and relativelyunobtrusive. In other implementations, sometimes called “blank andburst,” the voice is cut off while data is transmitted through the voicechannel. In still other implementations, portions of the audio frequencyspectrum are used for voice, while other portions are reserved for data.This aides in decoding at the receiving side.

In-band signaling requires appropriate facilities (e.g. an in-bandmodem) at both ends of the call. A challenge arises in detecting when toturn the modem on and off. That is, once a call is connected (linkestablished), when should the receiving system switch from voice mode ofoperation (using microphone and speaker typically), to a data mode inwhich it works to recover data from the audio (voice) channel?Preferably, this should be done automatically, i.e., without humanintervention. Prior art control signaling in a wireless network employsa control channel, which is not in-band. Unlike the voice channel,control channel signaling may be proprietary to the carrier andtherefore not available to all client systems.

One application of this technology, used for illustration in thisdocument, is communications with a motor vehicle. Today, many vehicleshave some capability for communications over a wireless networks. Werefer to these vehicle systems as a telematics client system. FIG. 2 isa simplified block diagram of an illustrative In-Vehicle System (IVS)21. It shows an example of the relevant portion of a typical telematicsclient system. This client system consists of embedded hardware andsoftware designed to operate in an automobile environment.

In FIG. 2, the telematics software 22 includes a “customer application,”23 which may be almost any application, in particular one that employsdata transfer via the wireless network. For example, the customerapplication may relate to navigation or entertainment. In operation, thecustomer application conveys data (preferably data packets) to anin-band signaling modem 27. The in-band modem 27 converts the data(along with packet headers and other overhead as appropriate) into audiofrequency tones, which are presented at the “PCM Switch” 25.

One purpose of the client system (IVS) 21 is to transfer telematics databetween a vehicle and a server over the same wireless voice call thatthe occupant uses to communicate with a human operator. Sometimes theserver is located at a “call taker center” where human operators may beavailable, similar to an emergency 911 call taker center. Here, thesystem must have a switch that disconnects the in-vehicle audio system26 at the beginning of an in-band modem session. If the switchingdecision is to be controlled from the server side, then the in-bandsignaling must be used to indicate when a modem session should begin.

Referring again to FIG. 2, in this embodiment the PCM switch 25 iscontrolled by an in-band “modem detection” scheme. There are two ways tomake a mistake: false detection (the speaker 29 is muted when itshouldn't be), and missed detection (the speaker 29 isn't muted when itshould be muted). Both kinds of errors should be as infrequent aspossible, yet it presents a challenge to avoid them. One importantadvantage of the present invention is improved detection performance.

FIG. 3 illustrates a progression over time of a first in-band modemdetection scheme. The given tone frequencies shown in the drawing areonly examples. In operation, the server 41 (located at a call takercenter, or “data center” which may be automated (unattended)), transmitsa predetermined audio frequency tone 42, for example 2225 Hz, which hasbeen selected to traverse the current vocoder technology. This is thesignal to the vehicle system to interrupt the voice conversation andbegin an in-band modem session.

After detecting this frequency tone 42 at the IVS side, for at least apredetermined threshold period of time, say about 30 msec, a“preliminary detection” is deemed accomplished, and the IVS 21 will mutethe speaker 31 (FIG. 2) in the vehicle. (In this way, the vehicleoccupants will not hear the “noise” of data transferring in the form ofaudio frequency tones 42.) If the selected “signaling tone” is detectedfor a longer than a predetermined threshold period of time, “Validation”is deemed to have occurred, and a “Response” is sent from the IVS 21 tothe server 41. Accordingly, the IVS 21 will switch the PCM switch 25 inFIG. 2 to couple the in-band modem 27 to the vocoder 24 in the embeddedphone module for data transmission (in the voice channel) to the datacenter.

The “Response” tone 44 has a second selected frequency, namely 1778 Hzin the illustrative example. It also has a selected duration, namely 300msec in the illustrative example. This is the signal that the IVS 21 isready to begin the in-band modem session. If the server 41 detects thissignal for at least a predetermined threshold period of time, say about200 msec then it (the server 41) stops transmission of the initiatingtone 42.

The foregoing strategy is useful for many applications, but a furtherproblem arises with changes in wireless technology. One area of frequentimprovement is in the vocoders mentioned above. As vocoders become moreefficient at coding human voice, it sometimes becomes even moredifficult to transmit data through the voice channel where thosevocoders are used. The in-band control signaling scheme described abovemay work fine for some vocoders, but not other, newer models.

One might address this problem by studying the characteristics of thenew vocoder, and then attempting to design a control signaling schemethat is compatible with the new vocoder. Even if that succeeds, however,there are many vehicles in use that still operate the older “legacymodem.” It is essential for a successful communication system that itoperates properly with both older IVS's (having legacy modems) as wellas newer ones that employ newer vocoders. The need remains to interactproperly with two or more different in-band modems as may be deployed invarious vehicles (or other portable applications, for example hand-heldpersonal communication devices). The “preliminary detection” tone at2225 Hz for example, described above, may work with an older vocoder butgets filtered out in a newer model. At best, the IVS would not mute thespeaker within the desired time. At worst, the in-band datacommunication system would fail.

The problem of backward and forward compatibility between a data serverand various mobile units is not limited to the control signaling. Theactual data transfers through some vocoders may require the use offrequencies quite different from those compatible with legacy vocoders.For example, with some legacy vocoders, 2100 Hz (downlink) and 2500 Hz(uplink) are useful frequencies for encoding data. For other vocoders,lower frequencies such as 1200 Hz and 1600 Hz may be preferred.

Thus it is essential for the server system to “discover” or detect thetype of remote vocoder in use on a particular call, not only for controlsignaling, but also so that it can encode data appropriately to survivethe remote vocoder. Moreover, it is important that the server veryquickly discover type of remote vocoder in use, for example in less thantwo seconds, so that it can send an appropriate control signal directingthe IVS to mute the speaker in the vehicle, before distracting datatones are heard. (In general, the incoming telephone number used tocontact the call center cannot be used to distinguish the remote modemin use because a single telephone number preferably is used for all IVSsystems of a given vehicle manufacturer.)

Refer to FIG. 4. For illustration, let us assume that a 2225-Hz tone iseffective as a control signal over an older vocoder channel, but that itis unreliable over a newer vocoder. In accordance with another aspect ofthe present invention, a frequency modulated (FM) tone 62 is transmittedby the server 61 to elicit the response tone 64, the FM signaloscillating between 500 and 600 Hz. It might switch frequency, forexample, every 20 or 40 msec; this describes the order of magnitude, theexact values are not critical. The frequency modulation is a key aspectin preventing false detections during regular voice conversation.

Refer next to FIG. 5: If the server 61 must be backward compatible withlegacy IVS modems, then it could alternate between the new initiating 62signal and the old one 42 (FIG. 2) while listening for both types ofresponse signals 64 and 44.

It will be apparent to those having skill in the art that many changesmay be made to the details of the above-described embodiments withoutdeparting from the underlying principles of the invention. The scope ofthe present invention should, therefore, be determined only by thefollowing claims.

1. A method comprising the steps of: providing an In-Vehicle System(IVS) including an in-band signaling modem in a vehicle for mobile,wireless voice and data communication, both the voice and datacommunications to occur over a single voice call via a voice channel ofa digital wireless communication network; the vehicle further includingan in-vehicle audio system for entertainment and communication uses; thein-vehicle audio system including a speaker and microphone; deploying acustomer application in the IVS, the customer application coupled to thein-band signaling modem for sending data via the in-band signaling modemduring a voice call; in the IVS, initiating the voice call via thedigital wireless communication network to a remote call taker location;at the call taker location, receiving the voice call initiated from theIVS; sending a predetermined signaling tone from the call takerlocation, via the voice call, to the IVS preparatory to an in-band datasession; and in the IVS, responsive to receiving the predeterminedsignaling tone, muting the audio system speaker so that occupants of thevehicle will not hear the sounds of data transferring in the form ofaudio frequency tones between the customer application and the calltaker location.
 2. The method according to claim 1 and furthercomprising: measuring a duration of the signaling tone; muting thespeaker only after the signaling tone duration exceeds a firstpredetermined threshold period of time.
 3. The method according to claim2 and further comprising: if and when the signaling tone durationexceeds a second predetermined threshold period of time longer than thefirst predetermined threshold period of time, transmitting apredetermined response signal to the call taker location to acknowledgethe signaling tone.
 4. The method according to claim 2 and furthercomprising: responsive to receiving the signaling tone, and during thesame voice call, commencing an in-band data session for sending datafrom the IVS to the call taker location via the voice channel of thedigital wireless communication network.
 5. The method according to claim4 and further comprising: transmitting a frequency-modulated tone fromthe call taker location to the IVS as the signaling tone for backwardcompatibility with older in-band modems.
 6. The method according toclaim 5 wherein the frequency-modulated tone alternates among aplurality of selected audio frequencies, the audio frequencies selectedfor compatibility with known vocoders, so that the signaling tone passesthrough the vocoders.
 7. The method according to claim 6 wherein thefrequency-modulated tone alternates between two selected audiofrequencies.
 8. The method according to claim 5 wherein thefrequency-modulated tone switches among selected audio frequencies at aselected period having an order of magnitude of approximately 20 msec to40 msec.
 9. The method according to claim 5 including, in the IVS,sending a response signal in response to recognizing any of the selectedaudio frequencies used for the signaling tone.
 10. The method accordingto claim 4 including automatically beginning the in-band data sessionafter a predetermined setup period that begins when a response signal isdetected at the remote location.
 11. The method according to claim 4wherein the call taker location is unattended.
 12. The method accordingto claim 3 wherein the response signal is an audio tone having apredetermined duration.
 13. The method according to claim 12 wherein theresponse signal predetermined duration is on the order of 300 msec. 14.The method according to claim 4 wherein the customer application sendslocation data in the data session via the in-band modem for the calltaker location to initiate emergency services.
 15. An In-Vehicle System(IVS) comprising: machine-readable memory for storing telematicssoftware; a processor for reading the machine-readable memory andexecuting the telematics software stored therein; the telematicssoftware configured for execution on the processor for sending andreceiving data via a voice channel of a digital wireless communicationnetwork; the telematics software including a customer application and anin-band signaling modem for encoding and decoding data sent from and tothe customer application; an in-vehicle audio system, the audio systemincluding a speaker and a microphone; an embedded phone module, thephone module configured for at least voice-channel communications viathe digital wireless communication network; a switch for controllablycoupling the in-vehicle audio system to the embedded phone module forvoice communications, or alternatively coupling the in-band signalingmodem to the embedded phone module for data communication, all during asingle voice channel wireless call; and the switch arranged to interrupta voice conversation, by coupling the in-band signaling modem to theembedded phone module to begin an in-band data session, and muting thespeaker of the in-vehicle audio system, in response to detecting apredetermined signal tone received via the embedded phone module duringa voice-channel call; wherein the predetermined signal tone hasapproximately a predetermined audio frequency.
 16. The IVS according toclaim 15 wherein the signal tone has at least a first predeterminedthreshold duration before the switch activates to mute the audio system.17. The IVS according to claim 16 wherein the predetermined audiofrequency is approximately 2225 Hz.
 18. The IVS according to claim 16wherein the first predetermined threshold duration is on the order of 30msec.
 19. The IVS according to claim 16 wherein the in-band modem sendsa predetermined response signal via the embedded phone module, duringthe same voice-channel call, if and when the received signal toneexceeds a second threshold duration longer than the first predeterminedthreshold duration.
 20. The IVS according to claim 19 wherein the secondthreshold duration is on the order of 300 msec.